In recent years, with the rapid development of electronic data devices, mobile data communication devices and mobile smart devices have rapidly propagated. Next-generation electronic systems are expected to be developed to the extent that they can be attached to or inserted into a human body beyond just being mobile. Particularly, an artificial electronic skin or a tactile sensor capable of being bent, extended and attached to the skin or body of a human or a flexure has been attracting attention.
According to a conventional pressure sensor technology, electric signal changes, such as a resistance, a capacitance, and a voltage (piezoelectric effect), of an active layer material caused by an external mechanical stimulus are converted into analog and digital signals to identify the kind and magnitude of the external mechanical stimulus. As a method for increasing the sensitivity of a sensor to a stimulus, the structure of the active layer material may be deformed to effectively recognize the external mechanical stimulus. Further, as a method for improving the mechanical properties of the device, a hybrid soft material may be used or the structure of metal and inorganic material may be controlled to be deformed by an external force. That is, such a pressure sensor recognizes a pressure as a change in electric signal caused by a change in contact area or a change in thickness during deformation of the active layer material.
However, if the pressure sensor recognizes a pressure using a change in electric signal caused by deformation of a material, a thickness change, and a contact area in response to an external mechanical stimulus in order to achieve high sensitivity, the pressure sensor shows a response only within a specific range depending on viscoelastic deformation of the material. That is, the pressure sensor recognizes a pressure only within a change in contact area and deformation of the material and thus shows a response in a narrow pressure range and is limited in application.
Further, a conventional flexible pressure sensor uses an active layer formed as continuous thin films, and, thus, it is difficult to perform patterning to a material of the active layer. As a result, there is a limitation to manufacture a high-density pressure sensor. That is, the high-density pressure sensor uses an inorganic material, and, thus, the mechanical properties of the sensor may be degraded or a process of patterning an organic material may be complicated and uneconomical.
In this regard, Korean Patent No. 10-1665191 (entitled “A multimodal tactile sensor emulating the perceptional mechanism and tissue structure of human skin”) discloses a skin sensor that senses various tactile sensations by emulating the mechanism in the human tactile organ and mechanical properties of human skin.